Reconfigurable optical add/drop multiplexers (ROADMs) perform routing, adding, equalization, and dropping of optical signal in an optical line system. ROADMs can include amplifiers for boosting the power of optical signals. Many common optical signal amplifiers have non-uniform gain characteristics, however. For example, an optical signal amplifier amplifying a broadband optical signal, such as a wavelength-division multiplexing signal, may not amplify all wavelengths of the signal equally. For an optical signal passing through multiple amplifiers in a ROADM, through two or more ROADMs, or through one or more line amplifiers between two ROADMs, the cumulative effect of non-uniform amplification can result in some wavelengths of the signal having too much power while other wavelengths have too little power. Equalization can be applied to flatten the optical signal based on feedback of the power spectral density of the signal. Traditionally, however, this has required a closed-loop system between terminal devices in communication with each other and sharing a common communication protocol, typically meaning that terminal equipment had to be vendor consistent to perform feedback-based control.